This invention is concerned with measuring devices and is more particularly concerned with an improved device for measuring the concentricity of a cylindrical or like configured workpiece.
It has long been the practice to employ a solid V-block to test the concentricity of cylindrical machined workpieces. The surfaces of such V-blocks suffer wear marks over a period of time due to friction between the block surface and the workpieces being tested. This is not a significant problem so long as the workpieces being tested are always of the same diameter. However, if the same block is being used to test a variety of workpieces having different diameters the wear patterns on the block could distort the accuracy of the measurement. To correct such a situation the V-block has to be reground, an operation which is time-consuming and costly, or replaced in its entirety. Further, the standard solid V-block has a longitudinal relief groove which is necessary to permit grinding of the V-surface. The presence of this groove prohibits the testing of workpieces having very small diameters of the order of about 0.125 inches or less.
The above disadvantages in solid V-blocks are well-recognized in the art but few attempts to them have been reported. Aldeborgh U.S. Pat. No. 1,401,119 shows a device for measuring the diameter of a workpiece rather than determining the concentricity thereof. The device includes a V-shaped body for receiving the workpiece. The walls of the V-shaped body are provided with replaceable wear plates. Mennesson U.S. Pat. No. 2,408,672 also shows a similar device with replaceable wear plates in the V-shaped member for receiving a workpiece.
Swanson U.S. Pat. No. 2,489,597 shows a device for determining the concentricity of a cylindrical workpiece having a plurality of outside and inside diameters. The supporting surfaces for receiving the workpiece are formed by the edges of replaceable blades. When wear of the edges occurs the blades need to be removed and reground or replaced.
Frindel U.S. Pat. No. 3,328,885 shows a V-block having pins welded to the surface thereof to form the surfaces for contacting a workpiece. The V-block forms part of a device which employs optical means for checking the linear profile of a workpiece.
In accordance with the present invention it has been found that the disadvantages associated with V-blocks hitherto available can be overcome in a simple but elegant manner which will now be discussed in detail.